ABSTRACT Understanding abiotic stress responses is one of the most important issues in plant research nowadays. Abiotic
stress, including excess light, can promote the onset of oxidative stress through the accumulation of reactive oxygen
species. Oxidative stress also arises when in vitro propagated plants are exposed to high light upon transfer to ex vitro. To
determine whether the underlying pathways activated at the transfer of in vitro grapevine to ex vitro conditions reflect
the processes occurring upon light stress, we used Vitis vinifera Affymetrix GeneChip (VvGA) and a custom array of genes
responsive to light stress (LSCA) detected by real-time reverse transcriptase PCR (qRT–PCR). When gene-expression profiles
were compared, ‘protein metabolism and modification’, ‘signaling’, and ‘anti-oxidative’ genes were more represented in
LSCA, while, in VvGA, ‘cell wall metabolism’ and ‘secondary metabolism’ were the categories in which gene expression
varied more significantly. The above functional categories confirm previous studies involving other types of abiotic
stresses, enhancing the common attributes of abiotic stress defense pathways. The LSCA analysis of our experimental
system detected strong response of heat shock genes, particularly the protein rescuing mechanism involving the cooperation
of two ATP-dependent chaperone systems, Hsp100 and Hsp70, which showed an unusually late response during
the recovery period, of extreme relevance to remove non-functional, potentially harmful polypeptides arising from misfolding,
denaturation, or aggregation brought about by stress. The success of LSCA also proves the feasibility of a custommade
qRT–PCR approach, particularly for species for which no GeneChip is available and for researchers dealing with
a specific and focused problem.